1. Field of the Invention
This invention relates generally to tool supporting and positioning turrets for metal working machines and the like and more specifically concerns a bidirectional electrically energized machine tool turret mechanism having a bidirectional electrical drive motor for selectively rotating and counter-rotating a turret drive shaft and a mechanism for locking and unlocking the turret indexing shaft responsive to position selection by an encoder.
2. Description of the Prior Art
It is well known that machining operations for various parts and objects require the use of a number of machining tools that are either moved against a work piece or maintained in a particular position or under particular control while the work piece is being moved such as by rotation, linear movement, etc. In order to enhance the productivity of various machine tools, a multi-position turret mechanism has been developed which can support a desired maximum number of machine tools and which can be indexed to position selected ones of the machine tools relative to a workpiece to be machined. In the past, these turret mechanisms have been largely of mechanical nature, requiring machinists to accomplish manual indexing. Though mechanically indexed turret mechanisms significantly enhance productivity of machine tools as compared to single tool-type metal working machines, it has been considered desirable to enhance productivity even more by providing mechanical turret mechanisms with power energized and encoder controlled indexing systems. Typically, power energized turret mechanisms are provided with reversible electric motors and are provided with an encoder mechanism having the capability of detecting the desired indexing position and to operate the motor at the proper rotational direction for reaching the desired turret position with the minimum amount of rotational movement. Virtually all electrically operated turret mechanisms have a tooth-driven, clutch mechanism in the gear driven shaft arrangement between the drive motor and the turret. Turret indexing is then accomplished by unlocking an indexing shaft and by then rotating the unlocked indexing shaft turret until the turret reaches its desired position. An indexing stop pin which is typically actuated by a solenoid, then engages within one of a plurality of indexing recesses of the indexing shaft to thereby lock the indexing shaft against further rotational movement, with the turret properly positioned as controlled by the encoder mechanism. It is well known that the tolerances of gears of the shaft drive mechanism and the inter engaging gear faces of the shaft locking mechanism must be closely controlled in order to provide a turret mechanism that is capable of performing quality work. If tolerances allow slight rotational movement of the main shaft and turret relative to predetermined turret positions at the location of the tools being supported by the turret, this slight rotational tool movement will be accentuated and thus will be quite significant. It is desirable therefore to provide an electric motor driven turret mechanism for machine tools having the capability for accommodating machine tolerances without materially increasing the cost of the turret mechanism so that the resulting turret mechanism will provide exceptionally high quality tool positioning and the resulting work performed by the machine tool can be of exceptionally high quality.